Russia warned of serious legal consequences Friday arising from U.S. Secretary of State John Kerry's comment that Moscow and Damascus should be investigated for war crimes as a result of their airstrikes on civilian targets in Syria.

At the State Department, U.S. officials sought to play down Kerry's remark as nothing new. The secretary used similar terms at the United Nations last month, when he denounced Russian and Syrian aerial bombings of hospitals and children as "flagrant violations of international law."

But Kerry escalated the rhetoric bluntly on Friday, declaring that this week's repeated attacks on Syrian hospitals "beg for an appropriate investigation of war crimes."

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The secretary was speaking at the State Department, alongside visiting French Foreign Minister Jean-Marc Ayrault. During a news briefing later in the day, State Department spokesman John Kirby said Kerry's statement did not represent "a change of tone" in U.S. views about Russia and Syria's tactics.

Kirby rebuffed reporters' repeated questions about whom Kerry would want to lead a war-crimes investigation. "The secretary is not getting ahead of a process," the spokesman said.

'Outrageous violations' cited

An attack on a Syrian hospital Thursday night reportedly killed 20 people and wounded 100. The aid group Doctors Without Borders said attacks this week on four major hospitals in opposition-controlled areas of Syria were "outrageous ... violations of humanitarian law" that were severely limiting civilians' access to medical care.

"Russia and the regime owe the world more than an explanation about why they keep hitting hospitals, and medical facilities, and women and children," Kerry said Friday.

"Kerry's statement — this is propaganda," said Russian foreign ministry spokesperson Maria Zakharova. "There are some very serious legal consequences behind this terminology, and I think that Kerry used all of these terms to inflame the situation."

Kerry earlier this week formally ended bilateral discussions with Russia on a potential military partnership in Syria, but he has since spoken on the telephone, at his request, with Russian Foreign Minister Sergei Lavrov about the situation in the war-torn country.

As many as half a million people have been killed in Syria since the beginning of the civil war there in 2011, and millions of people have been displaced.

Russia opposes Security Council action

Russia said it deems unacceptable a draft U.N. resolution put forward by France and Spain, demanding an end to airstrikes and military flights over Aleppo. Deputy Foreign Minister Gennady Gatilov said the French proposal politicizes humanitarian aid.

The U.N. Security Council received a private briefing Friday from U.N. Syria envoy Staffan de Mistura in Geneva, one day after he delivered an emotional appeal on the bloodshed: "I would then like to ask the Russian authorities and the government of Syria, please look at my eyes ... and the eyes of the world and the public opinion. Are you really ready to continue this type of level of fighting, using that type of weapons, and de facto destroy ... the ancient city of Aleppo, with its own 275,000 people, for the sake of eliminating 1,000 al-Nusra fighters?"

Diplomats said de Mistura repeated similar statements Friday to the Security Council. They described "very tense" discussions, with only council member Venezuela appearing to support Russia's account of its actions in Syria.

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"Staffan de Mistura was crystal clear. He could not be clearer," French Ambassador François Delattre told U.N. reporters after the meeting. "His message to the Security Council was, 'You must act, and you must act now.'"

Veto by Moscow is likely

Delattre said the draft resolution grew out of a week of "very hard, literally night and day" negotiations, and that France intends to press for a Security Council vote on Saturday.

"There is no time to waste," he said. "There is an absolute emergency in Aleppo."

While saying he would have to wait for instructions from Moscow, Russia's U.N. Ambassador Vitaly Churkin signaled a veto is likely. "I cannot possibly see how we can let this resolution pass," he told reporters.

"The French proposal is very hastily put together," Churkin added. "I frankly believe that it is designed not to make progress and take the situation out of the current stalemate or not to help Staffan de Mistura, but to cause a Russian veto."

He added that it is unprecedented for the council to ask a permanent member to limit its own activities.

"There are certain things which we may do or not do. We may fly or not fly. But definitely they cannot expect that we will go there through a demand by the Security Council," Churkin said. "It does not mean certain things cannot happen, but they can happen through a certain process."